1. Field of the Invention
The present invention relates to a composition, more specifically to a film forming composition, further specifically to a composition which is capable of forming a coated film having an appropriate and uniform thickness, and adapted for use as a material for an interlayer insulating film in a semiconductor device or the like, and which is also useful for forming an insulating film having excellent dielectric characteristics or forming an optical film of a low refractive index, a composition producing method, a film producing method, a film and a semiconductor device.
2. Description of the Related Art
As an interlayer insulating film for use in a semiconductor device and the like, a silica (SiO2) film formed by a vacuum process such as chemical vapor deposition (CVD) has been frequently utilized. Also recently, for the purpose of forming a more uniform interlayer insulating film, a coated-type insulating film, called an SOG (spin-on glass) film and principally constituted of a hydrolysis product of tetraalkoxysilane, is also being utilized. Also with an increase in the level of integration of semiconductor devices and the like, an interlayer insulating film of a low dielectric constant, called organic SOG and principally constituted of polyorganosiloxane, is also being developed.
However, even a CVD-SiO2 film, showing a lowest dielectric constant among the inorganic films, has a specific inductivity of about 4. SiOF film, recently investigated as a CVD film of low dielectric constant, has a specific inductivity of about 3.3 to 3.5, but this film involves a drawback of a high hygroscopic property, thus showing an increase in the dielectric constant in the course of use.
In such situation, there is also known a method of employing organopolysiloxane as a material for insulating film excellent in insulating property, heat resistance and durability, and of reducing the dielectric constant by adding a high-boiling solvent or a pyrolyzable compound thereby forming pores therein. However, such porous film, though the dielectric constant is lower by the porous structure, is associated with drawbacks of a lowered mechanical strength and an increase in the dielectric constant by moisture absorption. Also since mutually connected pores are formed, there is involved a drawback that copper used for wiring diffuses in the insulating film.
On the other hand, there is already known a proposal to utilize a siloxane compound having a cage structure for producing an insulating film (cf. JP-A-2005-154771), but this method, being incapable of sufficiently maintaining the cage structure at the preparation of a coating liquid or of an insulating film, has little density reducing effect whereby the dielectric constant cannot be lowered sufficiently.